The embodiment relates to a printed circuit board (PCB), and more particularly, a PCB including a first circuit pattern of which an upper portion has a curvature, a circuit pattern having a second circuit pattern formed on the first circuit pattern, and a top metal layer formed on the circuit pattern by electroplating and a method of manufacturing the same.
As the PCB is formed by printing a circuit line pattern on an electrical insulating board with a conductive material such as copper, the PCB is referred to as aboard just before electronic components are mounted thereon. That is, in order to mount various types of electronic components on the planar surface, the PCB refers to a circuit board having a planar surface on which a mounting position of each component is fixed and a circuit pattern connecting the components is fixedly printed.
Generally, a surface processing method for a circuit pattern included in the above-described PCB uses an organic solderability preservative (OSP) method, an electro nickel/gold method, an electro nickel/gold-cobalt alloy method, an electroless nickel/palladium/gold method, etc.
Here, the above-described surface processing methods is selected based on the purpose of operation, for example, a use for soldering, a use for wire bonding, a use as connectors, etc.
FIG. 1 shows cross-sectional views of a process sequence for describing a method of manufacturing a PCB according to a conventional art, and FIG. 2 is a view illustrating an upper surface of the PCB according to the conventional art.
Referring to FIG. 1A, first, an insulating layer 10 is provided, and a seed layer 20 is formed on the provided insulating layer 10.
Further, a mask 30 including an opening (not shown) which exposes at least a part of an upper surface of the seed layer 20 is formed on the formed seed layer 20.
Then, electroplating is performed based on the seed layer 20, and a circuit pattern 40 under which the opening of the mask 30 is buried is formed on the seed layer 20.
Then, referring to FIG. 1B, when the circuit pattern 40 is formed, a grinding process for planarization of an upper surface of the formed circuit pattern 40 is performed.
While performing the grinding process, at least a part of the upper portion of the circuit pattern 40 spreads inside of the mask 30, and thus, an upper end portion of the circuit pattern 40 includes a protrusion (not shown) protruding in a direction of the mask 30.
Then, referring to FIG. 1C, a preprocessing process for performing a surface processing process is performed.
Here, the preprocessing process is performed using an acid-based chemical for etching a surface of the circuit pattern 40. At this point, when the preprocessing process is performed, the etching is performed not only on the upper surface of the circuit pattern 40 but also on boundary surfaces of upper and side surfaces of the circuit pattern 40.
Thus, when the preprocessing process is performed, each corner portion 50 of the circuit pattern 40 has a predetermined curvature in a convex shape.
In other words, when the preprocessing process is performed, gaps are generated between the mask 30 and the circuit pattern 40.
Further, in the conventional art, with the gaps generated as shown in FIG. 2, a surface processing process is performed on the circuit pattern 40 to form a top metal layer 60.
However, when the top metal layer 60 is formed with the gaps generated, the top metal layer 60 is also formed on the corner portions 50 of the circuit pattern 40.
Accordingly, as shown in FIG. 2, the top metal layer 60 according to the conventional art may include a protrusion 70 protruding in a direction of a side surface of the circuit pattern 40, and this makes a big impact on the reliability of the PCB.